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Efficacy of heat-treated Lacticaseibacillus paracasei PS23 for individuals with long coronavirus disease-19 syndrome: a double-blinded randomized control pilot study

Wu SI, Lin CJ, Lin YJ, Lin IC, Hwang LC, Chen WL

Scientific reports, 2026

Abstract

Long coronavirus disease (long COVID) refers to symptoms that persist beyond the acute phase of SARS-CoV-2 infection. This study applied the World Health Organization (WHO) definition, which identifies post-COVID-19 condition as symptoms lasting at least two months and beginning around three months after confirmed infection. Given limited evidence on probiotic use for long COVID, we conducted a double-blind, randomized, placebo-controlled trial to evaluate the effects of heat-treated Lacticaseibacillus paracasei PS23 (HT-PS23) in individuals with confirmed COVID-19 and self-reported prolonged symptoms. Thirty-nine eligible participants were randomly assigned to receive either the heat-treated Lacticaseibacillus paracasei PS23 (HT-PS23) or placebo for six weeks. Assessments included validated neuropsychological tests (including executive function and working memory using Color Trails 1&2 and Digit Span and Coding), self-reported symptom scales of depression, anxiety, and quality of life, and blood biomarkers related to inflammation, immune response, and stress (e.g. cortisol, IFN-γ zonulin). After the six-week trial, HT-PS23 group showed notable improvements in cortisol level (p = 0.006), a reduction in errors of CTT2 (p = 0.018), and symptom severity related to breathing difficulties (p = 0.016) and appetite loss (p = 0.030) compared to the placebo group. HT-PS23 may be a feasible and well-tolerated intervention for relieving cognitive or physical symptoms associated with…

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Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design.

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